Vehicular interior lighting, e.g., dome lights, courtesy lights, glove box lights, foot-well lights, and other roof and side panel interior lighting, has generally been realized through the application of conventional, incandescent lighting sources for the past few decades. Although the light produced from incandescent sources is fairly uniform, it is generally accompanied by relatively high heat levels and low intensity compared to more modern light sources (e.g., light-emitting diode, fluorescent, etc.). Further, incandescent light sources have relatively high energy usage compared to more modern light sources.
In the past decade, light emitting diode (LED) sources have been employed in various lighting applications, including vehicular applications. LED sources possess many advantages over conventional lighting sources including the ability to transmit high intensity light patterns and generate low heat upon light transmission with very low energy usage. One drawback of LED sources is that the light produced from them is directional and can result in high-contrast illumination, shadowing and other undesirable effects associated with highly directional light. Consequently, in the context of vehicular interior lighting, LED sources have been difficult to use given that the directional nature of the light output from these sources has led to high contrast within the close quarters of the vehicle interior.
Some success has been realized in overcoming the directional nature of the light output from LED sources by coupling certain optics to them. In particular, near-field lens elements, collimators, light-diffusers and reflectors have been coupled to LED sources to shape their light output into uniform patterns approximating those produced by incandescent sources. Unfortunately, many of these solutions require additional packaging (e.g., larger overall lighting source dimensions) that can significantly add cost; consequently, LED sources are not prevalent in vehicular interiors, particularly as replacements to low-cost courtesy and dome lights.
Consumers are also increasingly demanding access to natural lighting within vehicles, residences, offices and other interiors. In vehicles, natural lighting that supplements the natural light transmitted through side windows, windshields, and rear windows is often provided through sun roofs, moon roofs and other non-traditional windows. Many consumers, however, find significant drawbacks associated with these supplemental natural light access points including the loss of interior space associated with the motors and elements needed for these natural light access points, maintenance and reliability concerns associated with their moving parts, and potential increased water leakage through them upon premature failure of their elements. Another drawback associated with moon roofs and sun roofs is that these elements reduce the amount of space available in the roof of the vehicle for dome and courtesy lighting.
Accordingly, there is a need for vehicular interior lighting solutions that can employ LED sources in a low-cost fashion, with minimal packaging constraints and at low manufacturing costs. Further, as LED sources continue to be integrated within the vehicle industry, there is a desire by many consumers for unique lighting aesthetics that cannot be achieved through conventional sources, including supplemental natural lighting for the interior of the vehicle.